Since tefilla is standing before the King, you must be fully dressed unlike Krias Shema that bedieved, it is sufficient to cover and seperate the ervah. (ShA 1 – MB 1,2 – BeH “yatza”)
If you wear a belt all day, keep it on for tefilla. But if you do not wear a belt, you don’t need to put one on unless you want to fulfil middas chassidus. (ShA 2 – MB 4)
The Zohar states that one who opens his eyes during tefilla causes the Malach Hamovves to come earlier. It also causes to lose the z’chus to see the Shechina at the departing of his soul. However, if one looks into a siddur this does not apply. (MB 6 – see MB 5 to siman 95)
Do not mention the Holy Name with a bare head. A straw hat is considered covered, so is your friend’s hand on your head. Although your own hand doesn’t suffice, pulling your shirt sleeve up and on top of your head does suffice. (ShA 3,4 – MB 10)
Do not daaven to Hashem wearing something less respectful than that which you would wear to a meeting of an important political leader. This criterion is constant but its application changes from country to country. (ShA 5 – MB 11,12)
The proper way for chachomim and their students is to be wrapped (with a tallis or hat and jacket) for tefilla. (ShA6 – MB siman 183:11)